Mixed connective tissue disease

A 34-year-old woman comes to the office because of a purplish rash on her face that is most prominent above her eyes. She reports that a few years ago, her fingers become painful and blue when she went outside without gloves. She has also had pain in her elbows and knees, but uses ibuprofen to alleviate symptoms. She denies muscle weakness, difficultly swallowing, palpitations or fever. Her lung examination is notable for a rubbing sound, but the rest of her exam is within normal limits. Which of the following antibodies is most likely present causing her symptoms?